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Summary: Motion Compensation for Temperature Imaging using the Change in Ultrasonic
Backscattered Energy
Yuzheng Guo
Jason W. Trobaugh
R. Martin Arthur
Abstract
Background. Ultrasound is an attractive choice for noninvasive thermometry to enhance tumor treatment
using hyperthermia. Our theoretical model [1] predicted and in-vitro experiments [2] verified that the
change in backscattered ultrasonic energy (CBE) is monotonic (approximately 0.2~0.3dB/oC) with
temperature in the hyperthermia range, motivating the usage of CBE for ultrasonic thermometry. One
limitation in measuring temperature-dependent CBE from ultrasound images is apparent motion in the
images due to change of the speed of sound and motion of the tissue. Previously, a block-matching
motion-tracking method was used to compensate rigid motion but was only successful for small regions
[2].
Methods. We have developed an algorithm for estimating and compensating non-rigid motion over large
2D or 3D regions. The motion field was modeled to vary linearly over the region of interest and was
estimated by maximizing the cross-correlation between the reference and subsequent images using
optimization functions in MATLABŪ. Factors affecting performance of the algorithm were studied using
simulation of images for multiple scatterers [3]. Images before and after motion were simulated by
transforming scatterer locations.
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